GOCROWEEN Flange Inserts 13/15/17/19/21mm (5pcs Pack) are using for finding the right size for your nipples,compatible with Medela PersonalFit 24mm Shields,Spectra 24mm flanges,Momcozy S12 pro/S9 pro/S9/S10/S12 Wearable Breastpump 24mm cups.It will reduce the 24mm shield nipple tunnel down to Correct Size(not for 27mm shield) Compatibility with Momcozy S12 pro/S9 pro/S9/S10/S12 Wearable Breast Pump,example for Momcozy,TSRETE,Luxlady,HAUTURE,eulumap,CPPSLEE, Cupood,Fisroa,Goldeep,Zybeauty,PADRAM,HAHOME,Kompoll,OMFMF,Paruu,LRKHFFD,Mumeasy. This replacement part is also applicable to most other brands of the models for 24-25mm (Freemie),and compatible with MISSAA hands-free breastpump. The size of your flange insert is important for comfort and efficient pumping.Some moms have the experience of nipple swelling while milking, so it is important to observe the appearance of the nipple during pumping. The flange insert is recommended to be replaced every 1 to 2 months.Please choose the right size . BPA free,made of food-grade silicone,easy to clean. 0